DESCRIPTION (from applicant's abstract): The long term objective of this project is to elucidate the molecular and cellular biology dopamine transporter (DAT), a plasma membrane protein thought to control synaptic levels of the neurotransmitter dopamine. Many of the effects of cocaine and other psychostimulants are mediated through interaction with the DAT. Since there are apparently major differences in the cocaine-responsiveness of the DAT in rat and human brain, it is necessary to accurately describe the nature of cocaine-induced changes in the DAT in human brain before this phenomenon can be successfully modeled. The proposed experiments will determine changes in the abundance of DAT mRNA and DAT protein in well- characterized postmortem tissue from cocaine overdose victims using quantitative in situ hybridization histochemical, radio- immunocytochemical and immunobloting techniques. Studies will be then extended to include the serotonin and norepinephrine transporters, physiologically important but understudied cocaine-binding proteins. We have recently sequenced a portion of the human DAT gene and tentatively identified a number of potential regulatory elements. The transcription factor(s) which may underlie the cocaine-responsiveness of the DAT gene will be identified by quantification of transcription factor protein, mRNA and binding activity within human DA cells in cocaine overdose victims and matched control subjects. An understanding of DAT regulation and cocaine-induced changes in human DAT gene expression may shed light on the molecular basis of cocaine addiction, an affliction affecting greater than 1% of the U.S. population. Elucidating the regulation of the DAT may shed light of other pathophysiological states as well, since DAT expression is altered in Parkinson's disease, Alzheimer's disease, normal aging, schizophrenia, Tourette's syndrome, and Lesch-Nyhan disease.